1. Field of the Invention
The present invention relates to drug delivery devices. More particularly, the present invention relates to needle and hub assemblies for automatic injection devices.
2. Description of Related Art
Many types of syringes and other injection devices are used in the medical device arts. Typical syringes, for example, use a hollow needle to deliver a medicament subcutaneously, intramuscularly, or intravenously to a patient. The needle is usually connected to the portion of the syringe that holds the medicament by a hub assembly. The hub assembly secures the needle and also supports it.
An automatic injector is a type of injection device that enables intramuscular (IM) or subcutaneous administration a dose of medicament. In the typical automatic injector, a cartridge carries the dose of medicament and is connected to a needle assembly. The cartridge and needle assembly are contained within a housing, which also carries an actuation assembly. When the actuation assembly is activated, the needle is caused to penetrate and protrude from the housing and the medicament is caused to be injected into the patient. Thus, automatic injectors allow for quick and simple IM injection of a medicament in emergency situations without the need for measuring dosages. Additionally, automatic injectors are convenient for self-administration of medicament, because the user does not see the needle before actuation of the device, and there is no need to manually force the needle into the patient.
There are three main types of automatic injectors. A first type is that which carries its medicament mixed in liquid form. A second type of automatic injector, called a “wet/dry” automatic injector, has two separate compartments and carries its medicament in the form of two components, a dry component and a liquid component. When the actuation assembly is activated, structure within the cartridge of the automatic injector forces the dry and liquid components of the medicament to mix. A third type of automatic injector, called a “wet/wet” automatic injector, has two separate compartments and carries its medicament in the form of two liquid components. The wet/wet automatic injector includes structure within the cartridge that may force the two components to mix when the actuation assembly is activated or the automatic injector may deliver the fluid consecutively.
In one common arrangement of an automatic injector, one of the medicament compartments is directly adjacent to the needle assembly. During manufacture, the compartment adjacent to the needle assembly is filled with a medicament component and the needle assembly is installed over the opening in the compartment to seal it. The needle assembly includes a needle hub and the needle itself. With this sort of arrangement, it is beneficial if the opening in the cartridge and the compartment is as wide as possible, because wide openings allow for easier filling of the compartment with the medicament, especially when the medicament or component is in the form of a dry powder or a lyophilized tablet. However, the size of the opening is limited in practice because it is difficult to make a needle assembly that can seal the compartment well and support the needle adequately.